The present invention describes granulocyte-binding antibody constructs, which were derived from the monoclonal mouse antibody Mab BW 250/183 (EP-A1-0 388 914), as well as a process for their preparation and their use.
The monoclonal antibody Mab BW 250/183 is a monoclonal mouse antibody of the IgG1 kappa type which is directed against the "nonspecific crossreacting antigen"(NCA)95 and against the carcinoembryonic antigen (CEA) and does not have any unwanted cross reactions with normal human tissues apart from the colon mucosa. Its binding to granulocytes and granulocyte precursors in the bone marrow also makes a therapeutic application possible.
Usually, antibodies which were isolated from rodents, in particular mice, are used in the therapeutic application of monoclonal antibodies (Mabs) in humans. However, the repeated administration of high doses of antibodies of non-human (xenogenic) origin can lead to an immune reaction in the patients. After about 10-14 days they develop anti-mouse immunoglobulin antibodies (HAMAs). A therapy of this nature must therefore be discontinued after 10 days and cannot be reinitiated.
In the meantime, success has been achieved, with the aid of molecular biological methods, in altering the xenogeneic antibodies in such a way that they are either no longer or only very weakly immunogenic for humans but nevertheless preserve their antigen-binding properties. To do this, the constant exons (CH.sub.1, H, CH.sub.2, CH.sub.3, CL) in the genes encoding the H and L chains of the xenogeneic Mabs were exchanged, in a first step, for exons from human immunoglobin genes (Boulianne, G. L., Nobumichi Hozumi, and Marc J. Shulman (1984) Nature 321, 643-646). In this way, so-called chimeric antibodies are obtained which are composed of variable domains of xenogeneic origin and human constant regions. These chimeric antibodies still contain about 30% of xenogeneic protein sequences so that when they are used in immunotherapy an immune reaction, even if weaker, is still to be expected in the patients (Bruggemann, M., Greg Winter, Herman Waldmann, and Michael S. Neuberger (1989) J. Exp. Med. 170, 2153-2157).
In order to reduce the immunogenicity of xenogeneic antibodies still further, a technique was developed by G. Winter and M. Neuberger (1986) in which only the CDR loops of the V.sub.L and V.sub.H domains of the xenogenic antibodies are transferred to V.sub.L and V.sub.H domains of human antibodies (Jones, P. T., Paul H. Dear, Jefferson Foote, Michael S. Neuberger, and Greg Winter (1986) Nature 321,522-525), a process which is termed "humanization" and takes place at the level of the V.sub.H and V.sub.L genes. The structural variability of the V.sub.H and V.sub.L domains is in general confined to the CDR loops ["CDR" stands for complementarity-determining regions].
In the present patent application, antibody chains are now described which are specific for human granulocytes and in which at least the CDR regions of the heavy and light chains derive from the mouse Mab BW 250/183 (EP-A1-0 388 914). The remaining parts of molecular constructs prepared thereby, e.g. monoclonal antibodies, are preferably derived from human antibodies.